Crossword Genius

With ire, guy is interrupting leader's unionist idea (3-9)

Ross

I believe the answer is:

pan-germanism

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'unionist idea' is the definition.
The definition suggests a singular noun which matches the answer.

'with ire guy is interrupting leader's' is the wordplay.
'with' indicates putting letters inside.
'ire' becomes 'anger' (synonyms).
'guy' becomes 'man' (guy can informally mean a man).
'is interrupting leader' becomes 'pism' (I can't justify this - if you can you should give a lot more credence to this answer).
'anger'+'man'='angerman'
'angerman' inserted within 'pism' is 'PAN-GERMANISM'.

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